Found a way to fix intermittent boot failures by checking the CMOS battery voltage first

Been dealing with a Dell OptiPlex that would randomly not POST for weeks. Turns out the CR2032 was down to 2.8V, swapped it for a fresh one and it's been solid for 5 days now. Anyone else skip the battery check and waste time on other parts first?

2 comments

2 Comments

oscarwright1d ago

@elliots49 nailed it with that Z220 story. The battery voltage thing is one of those traps that hits everyone at least once. What I'm curious about though is what voltage level actually starts causing the issue in your experience? I've seen boards act flaky anywhere from 2.8V down to 2.5V, but I've also had a couple that still ran fine at 2.6V for months. Like is there a hard cutoff where the CMOS just stops saving stuff right, or does it vary board to board? Been meaning to actually test that with a bench power supply.

elliots491d ago

Totally been there. Spent a weekend swapping RAM sticks and reseating the GPU on an old HP Z220 before I thought to check the voltage on the CMOS. Reading 2.7V on my multimeter. Dropped in a new battery and it booted up first try every time since. Now I always poke the battery first on any old board before messing with anything else. Saves so much headache when you realize the BIOS is just getting corrupted from low voltage and not saving the hardware config right.